I thought I had made this clear, but apparently not.
What you have described above simply does not happen (or if it does, I have not come across it).
With a competent client, with whom you have a good and continuing relationship, you might go through the work in a summary fashion (this will still take a half an hour) in a face to face meeting.
You might explain that based on the information which you have both reviewed at that meeting, it looks like the bill is going to come in at a minimum of €X.
Crucially, the client will have seen more than enough information at this point to be able to agree and accept that this is indeed the case.
At that point, the transparent and pragmatic solicitor and the informed client are perfectly free to make an agreement based on the solicitor saying "how about I just charge you €Y" and the client saying "yeah, seems fair enough, go ahead".
No solicitor with half a brain would issue a bill saying "it's this amount if you agree, but more if you query it".
No client with half a brain would accept that sort of thing.